Uncertain Murder. Watchbearers, #3

-A Sam and Bailey Mystery In the summer of 1992, tech billionaire Brandt Keener dies drinking a glass of wine while dining with his nearest if not dearest on his small private island off the Washington coast. Despite suspicious circumstances and an abundance of motives, the police find no evidence of homicide, and three weeks later the same people who were present at his death gather again for the reading of his will.
Convinced the man was murdered, time-travelers Sam and Bailey inveigle themselves onto the island to investigate, but their best suspects soon start dying. The series continues with Book 4: Prohibited Activities, Book 5: Temporal Entanglement, and Book 6: Belated Witness, the second Sam and Bailey mystery.